package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    @Autowired
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
//        Shop shop = queryWithLogicalExpire(id);

        //---------------封装工具类解决------------------

        // 解决缓存穿透
        Shop shop = cacheClient
                .queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 互斥锁解决缓存击穿
        // Shop shop = cacheClient
        //         .queryWithMutex(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 逻辑过期解决缓存击穿
        // Shop shop = cacheClient
        //         .queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.SECONDS);


        if (shop == null) {
            return Result.fail("店铺不存在..");
        }

        return Result.ok(shop);
    }

    /**
     * 逻辑过期解决缓存击穿
     *
     * @param id
     * @return
     */
    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        // 1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isBlank(json)) {
            // 3.存在，直接返回
            return null;
        }
        // 4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 5.1.未过期，直接返回店铺信息
            return shop;
        }
        // 5.2.已过期，需要缓存重建
        // 6.缓存重建
        // 6.1.获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.2.判断是否获取锁成功
        if (isLock) {
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unlock(lockKey);
                }
            });
        }
        // 6.4.返回过期的商铺信息
        return shop;
    }

    /**
     * 基于互斥锁解决缓存击穿
     *
     * @param id
     * @return
     */
    public Shop queryWithMutex(Long id) {
        //从redis查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //判断缓存中是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中是否是空置
        if (shopJson != null) {
            return null;
        }

        //实现缓存重建
        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //判断是否获取成功
            if (!isLock) {
                //失败则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }

            //TODO 获取成功应该再次检测redis
            //判断缓存是否存在
            //存在，则直接返回

            //不存在，根据id查询数据库
            shop = getById(id);
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //不存在，返回错误
                return null;
            }
            //存在，写入redis，需设置过期时间
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //释放锁
            unlock(lockKey);
        }
        //返回
        return shop;
    }

    /**
     * 解决缓存穿透
     *
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id) {
        //从redis查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //判断缓存中是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中是否是空值
        if (shopJson != null) {
            return null;
        }
        //不存在，根据id查询数据库
        Shop shop = getById(id);
        if (shop == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            //不存在，返回错误
            return null;
        }
        //存在，写入redis，需设置过期时间
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    /**
     * 尝试获取锁使用的是redis的setnx方法
     *
     * @param key
     * @return
     */
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    public void saveShop2Redis(Long id, Long expireSeconds) {
        //查询店铺信息
        Shop shop = getById(id);
        //封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        redisData.setData(shop);
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 释放锁
     *
     * @param key
     */
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    /**
     * 更新店铺信息
     *
     * @param shop
     * @return
     */
    @Override
    @Transactional
    public Result updateShop(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //更新数据库
        updateById(shop);
        //删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
